Hand-held machine tool comprising a dust box

ABSTRACT

A power tool ( 10 ) with a housing ( 12 ) that includes a dust box ( 50, 150 ) and a motor ( 20 ) with air cooling, and a cooling exhaust-air duct ( 44, 46 ) and a chip suctioning duct ( 40 ) which guides a chip-suctioning flow can be used with improved performance and in an environmentally friendlier manner due to the fact that the cooling air flows across the dust box ( 50, 150 ) under favorable flow conditions, whereby the evacuation of dust into the dust box ( 50, 150 ) is improved and whirls of dust caused by cooling air in the tool region are prevented from forming.

CROSS-REFERENCE

The invention described and claimed hereinbelow is also described inPCT/DE 03/02668, filed Aug. 7, 2003 and DE 102 54 839.0, filed Nov. 25,2002. This German Patent Application, whose subject matter isincorporated here by reference, provides the basis for a claim ofpriority of invention under 35U.S.C. 119 (a)-(d).

BACKGROUND OF THE INVENTION

The present invention relates to a power tool with dust box.

A power tool with motor air-cooling is made known in U.S. Pat. No.4,209,069, the cooling air of which is suctioned through the dust box. Adust filter is located between the dust box and the cooling ventilatorto prevent dust from entering the interior of the motor with the coolingair. In addition, a chip suctioning tube extends from the power tool tothe dust box. The chips and dust produced when a tool engages in a workpiece are transported to the dust box through this tube.

The disadvantage of this is that the cooling air flow is restricted bythe high resistance of the dust filter located upstream of the coolingventilator. Dust filters cannot be eliminated, however, since dustentering the motor with the cooling air impairs the motor function. Inaddition, the cooling exhaust air exiting the motor housing causesunhealthy whirls of dust in the chip-removing region of the tool.

SUMMARY OF THE INVENTION

The present invention has the advantage that the cooling exhaust air cannot exit the housing directly and enter the surrounding air. Instead,the cooling exhaust air is directed over the dust box under favorableflow conditions, thereby exiting the housing in an unthrottled manner;the dust evacuation into the dust box is simultaneously improved and thecooling exhaust air is prevented from swirling the dust in the toolregion. In addition, chip evacuation in the region of the toolengagement is improved via the injector action of the coolingexhaust-air flow directed over the dust box.

Due to the fact that the cooling exhaust air is guided separately fromthe dust evacuation air away from the housing to the dust box and pastit in an unthrottled manner, the efficiency of the motor cooling is highand uncompromised.

Due to the fact that a suction connecting piece of the housing directsthe dust evacuation air separately from the cooling exhaust air, the twoair streams are prevented from mixing, ensuring highly efficient dustevacuation and, simultaneously, motor cooling.

Due to the fact that the dust box includes an air outlet opening forboth the dust evacuation air and the cooling exhaust air on its backend, the cooling exhaust air must pass over its entire top side andexercise its full effect as a vacuum pump, resulting in a markedimprovement in dust evacuation.

Due to the fact that the horizontally longitudinally divided dustevacuation-air branch of the power tool has an inlet opening, locatedradially outwardly and at the top, to the cooling exhaust-air ductformed in the top part of the dust evacuation-air branch, the coolingexhaust air can be easily guided further to the dust box and across itsouter surface.

Improved dust evacuation into the dust box is realizable due to the factthat the dust box includes a coupling branch that fits the dustevacuation-air branch and is capable of being joined therewith, and thecooling exhaust-air duct of the dust box is capable of being coupledwith the dust evacuation-air branch, the dimensions of which are matchedto those of the cooling exhaust-air duct.

Due to the fact that the dust box is provided with a base capable ofbeing detached in the manner of a cover, it is particularly easy toempty.

Due to the fact that the dust box also includes a top wall capable ofbeing detached in the manner of a cover, it is particularly easy toremove together with the filter, so it can then be tapped to easilyremove the dust.

Due to the fact that the cooling exhaust-air flow must exit the housingtangentially through a cyclone-like annular exhaust air duct, flowresistance of the cooling exhaust-air flow is reduced, and noise isdampened. As a result, particularly high vibration frequencies of thecooling exhaust air are suppressed.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is explained in greater detail below withreference to an exemplary embodiment with associated drawing.

FIG. 1 shows a longitudinal sectional view of a disk-type sanderaccording to the present invention.

FIG. 2 shows a longitudinal sectional view of a dust box according tothe present invention,

FIG. 3 shows a front view of the dust box according to FIG. 2, and

FIGS. 4 and 5 show tubular, longitudinally-divided coupling branches ofthe dust box.

DETAILED DESCRIPTION OF THE OF EXEMPLARY EMBODIMENT

The drawing shows a power tool 10 designed as a disk-type sander with ahousing 12 that has a horizontal handle 14 shown at the left in thedrawing, the handle including a manually-operated switching key 16 of aswitch (not shown) for starting and stopping motor 20.

An electric cord 18 extends out of the back end of handle 14, theelectric cord providing power to motor 20.

Housing 12 carries motor 20 with a motor axis 19 extendingperpendicularly to handle 14, in the downward extension of which a motorshaft 22 projects out of motor 20. Its end is wrapped-around in atorsion-proof manner by a cooling ventilator 26 that moves air radiallyoutwardly in the direction of arrow 48. As a result, cooling outside airis drawn in via the upper region of housing 12 through cooling slits 23in housing 12; the cooling outside air can flow into housing 12 asindicated by arrow 24 and past motor 20, and then exit housing 12 viaits suction connecting piece 42 through a connecting duct 46.

Connecting duct 46 extends to the end of suction connecting piece 42 andis sealed off from it. This is achieved via a separate partition 49which prevents the cooling exhaust air from mixing with the dustevacuation air in the suction connecting piece. As a result, the coolingexhaust air can exercise its suction effect by flowing across the outersurfaces of dust box 50. When dust box 50 is attached and couplingbranch 52 is slid over suction connecting piece 42, an axis-parallelpartition 58 of dust box 50 grips underneath partition 49 of suctionconnecting piece 49. As a result, dust evacuation air can enter dust box50 via dust evacuation-air duct 40 without swirling and without flowlosses and exit the dust box cleaned of dust. To this end, the dustevacuation air passes through a pleated filter 64 located on the topside of dust box 50, in particular tightly bonded with its top cover 42,whereby the exhaust air, cleaned of dust, can pass through a largenumber of air holes 72 in cover 62 and exit dust box 50 through airoutlet opening 70. Air outlet opening 70 is formed between the rear edgeof cover 62 and a hood 66 that extends over it. On the sidediametrically opposed to the air outlet opening, hood 66 transitionsinto coupling branch 62 and forms the top side of cooling air duct 54 ofdust box 50. Air holes 72 on the top of dust box 50 are partiallycovered by small spoilers 54, over which the cooling exhaust-air flowsrapidly and without swirling, and which helps create a stronger vacuumwhen cooling exhaust-air flows past air holes 72. As soon as motor 20 ofpower tool 10 is switched on and cooling exhaust-air flows over cover 62of dust box 50, a stronger exhaust air flow forms due to air holes 72;this markedly strengthens the dust-evacuation air flow all the way backat dust-suctioning holes 38 in grinding wheel 34, thereby increasing theamount of dust in the air surrounding power tool 10 and increasing theefficiency of grinding work by allowing the abrasive particles to engagemore directly in the work piece without being inhibited by grindingdust.

Housing 12, which encloses cooling ventilator 26, is sealed off axiallyat the bottom and is penetrated by the lower end of motor shaft 22. Itis rotatably supported there in a rolling bearing 28.

In the bell-shaped region facing away from cooling ventilator 26, thefree end of motor shaft 22 includes a dust ventilator 30 that suctionsin air and/or chips through dust-suctioning holes 38 in grinding wheel34 and blows them out to suction connecting piece 42.

An annular sealing lip 51 seated on the lower edge of housing 12 bearsagainst the top of grinding wheel 34 resiliently and pretensioned in theaxial direction. The space between housing 12 and grinding wheel 34 istherefore sealed off from interfering inleak air, and highly-efficientchip evacuation is ensured.

At the bottom, toward grinding wheel 34, dust ventilator 30 includes aneccentric opening (which is not described in greater detail) thatfunctions as a bearing seat for a ball bearing 31. Eccentrically seatedball bearing 31 supports an eccentric pin 32 that is capable of beingconnected in torsion-proof fashion with grinding wheel 34 via a screw36.

When motor shaft 22 rotates, eccentric pin 32—and dust ventilator30—follows this rotation due to its bearing friction and/or that of ballbearing 31 by rotating around its eccentric axis while simultaneouslyencircling motor axis 19 and/or motor shaft 22. This results in thecharacteristic orbital oscillating motion of grinding wheel 34, which istypical of disk-type sanders.

FIG. 2 shows a longitudinal sectional view through a further exemplaryembodiment of a dust box 150, the cover-like base 160 of which isdetachably positioned, thereby enabling convenient removal of dust fromdust box 150. Coupling branch 152 is shown on the left side in thedrawing; it has a divided configuration and is composed of a topcooling-air duct and a bottom dust air duct, which is formed by acooling exhaust-air branch 352 and a dust evacuation-air branch 252extending axially past it. Cover 162 is diametrically opposed to base160, and it transitions as a single piece into side walls 68 of dust box150.

On its top side, cover 162 includes a large number of evenly distributedair holes 172 located side-by-side that are provided, on the side facingcoupling branch 152, with a large number of gill-like spoilers 174slanted toward the opposite side, over which cooling exhaust air blownin through cooling air duct 54 flows with minimal flow loss, whereby thevacuum effect at air holes 172 is increased, thereby enablingparticularly effective dust evacuation from grinding wheel 34 into dustbox 150.

Air holes 172 are covered in a dust-proof manner by pleated paper filter164 on the inside of dust box 150, so that the dust evacuation air whichcarries the dust has no other way out of dust box 150 than throughpleated filter 164. The dust evacuation air is moved out via a certainoverpressure in the interior of dust box 150 and a vacuum which existsabove air holes 172.

A slot which extends nearly across the entire width of dust box 150 andfunctions as air outlet opening 170 is formed on the right side (asshown in the drawing) between the top side of hood 166 and cover 162.

FIG. 3 shows a front view of dust box 150, whereby the coupling branchformed of cooling exhaust-air duct 352 and dust evacuation-air duct 252is capable of being coupled with suction branch 42 of power tool 10.Detachable, cover-like base 160 is shown on the underside of dust box150; after it is opened, dust box 150 can be conveniently cleaned ofdust.

FIGS. 4 and 5 show round-cylindrical coupling branches 552, 852 withlongitudinally extending partition 558, 858, via which a separateguidance of the cooling exhaust air and dust evacuation air is ensuredin the upper cooling exhaust-air ducts 752 or the dust evacuation-airduct 656 and/or 956 located below it, each of which is separated fromthe duct above it by a partition 558 or 858.

Corresponding to round-cylindrical coupling branches 552, 862, theconfiguration of suction branches of housing 12 must also beround-cylindrical in shape with a corresponding longitudinally-orientedpartition, so they can be inserted into each other.

1. A power tool (10) with a housing (12) that includes a motor (20) withair cooling and a cooling-air exhaust duct (48), and a suctionconnecting piece (42) that guides cooling exhaust air guided by thecooling-air exhaust duct as well as dust evacuation air, and, connectedthereto, a dust box (50, 150) including a top wall with air holes (72,172) and a base, wherein the dust box supports an air-tight hood inparallel with but a distance from the top wall and the base, and whereinthe dust evacuation air is guided in the suction connecting piece (42)of the housing (12) such that it is sealed off by a partition (49) fromthe cooling exhaust-air flow.
 2. The power tool as recited in claim 1,further comprising separated channels for guiding the cooling exhaustair and the dust evacuation air in separate air streams out of thehousing (12) to the dust box (50, 150) and further, unthrottled over itsair holes (72, 172) over a large surface area as in a flat duct.
 3. Thepower tool as recited in claim 1, wherein the air-tight hood (66)includes an air outlet opening (70) in its back end.
 4. The power toolas recited in claim 1, wherein the suction connecting piece (42) has aninlet opening for the cooling-air exhaust duct (48) located radiallyoutwardly and on an upper part of the suction connecting piece (42),that is guided in the upper part of the suction connecting piece (42).5. The power tool as recited in claim 1, wherein the dust box (50, 150)includes a coupling branch (52, 152) for connection with the suctionconnecting piece (42) of the power tool (10), the cooling air duct (54,154) of which is capable of being coupled with the cooling exhaust-airguided by the suction connecting piece (42).
 6. The power tool asrecited in claim 1, wherein the base of the dust box (50, 150) iscapable of being detached in the manner of a cover.
 7. The power tool asrecited in claim 1, wherein the top wall (62) of the dust box is capableof being detached in the manner of a cover, the top wall carrying apleated filter (64).
 8. The power tool as recited in claim 1, whereinthe cooling exhaust-air duct (46) is enlarged in the manner of a funnelin the outflow direction and, at its largest cross section, leads intothe suction connecting piece.
 9. The power tool as recited in claim 1,wherein cooling exhaust air flows in the space between the top wall ofthe dust box and the air-tight hood.
 10. The power tool as recited inclaim 1, wherein dust evacuation air flows in the space between the topwall of the dust box and the base of the dust box before it passesthrough the air holes in the top wall of the dust box to enter the spacebetween the top wall of the dust box and the air-tight hood.